Method and device for realizing ip multimedia subsystem disaster tolerance

ABSTRACT

A method for realizing an Internet protocol (IP) multimedia subsystem (IMS) disaster tolerance includes the steps as follows. An S-CSCF receives a user registration, and backs up necessary data which is required when a user service processing is restored on a storage entity in a network. An I-CSCF of user&#39;s home domain receives a service request of the user, and if it is found that the S-CSCF currently providing a service for the user fails, assigns a new S-CSCF to the user, and forwards the service request to the newly assigned S-CSCF. The newly assigned S-CSCF interrogates and acquires subscription data of the user and the necessary data backed up by the original S-CSCF from the storage entity, and then restores the user service processing according to the subscription data and the backup data. A device for realizing an IMS disaster tolerance is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CN2007/070943, filed Oct. 23, 2007, which claims priority toChinese Patent Application No. 200610150721.6, filed Oct. 24, 2006, andChinese Patent Application No. 200710135727.0, filed Aug. 10, 2007, allof which are hereby incorporated by reference in their entirety.

FIELD OF THE TECHNOLOGY

The present invention relates to a network disaster tolerance technique,and more particularly, to a method and a device for realizing anInternet protocol (IP) multimedia subsystem (IMS) disaster tolerance.

BACKGROUND

An IMS occupies a pivot position in the service processing for acommunication network, and the high reliability of the IMS is the basisof the high reliability of the whole communication network. A servingcall session control function (S-CSCF) serving as a network element (NE)for controlling the user service processing in the IMS acts as a core ofthe whole network service processing, so that a disaster tolerancecapability of the S-CSCF is quite important to the high reliability ofthe IMS.

FIG. 1 is a flow chart that a user who intends to get access to an IMSnetwork subscribes and registers in the IMS network in the conventionalart.

In FIG. 1, once the user initiates a registration (1. REGISTER) at aterminal, a register request message is sent to a proxy CSCF (P-CSCF)assigned to the terminal by an access domain so as to enter an IMSsubsystem. The P-CSCF forwards the register request to an interrogatingCSCF (I-CSCF) of user's home domain according to a domain identity ofthe user ( 2. REGISTER).

The I-CSCF interrogates from a home subscriber serve (HSS) of the userhome domain (3. UAR˜4. UAA), and a UAR message carries attribute valuepairs (AVPs) as follows: Public-Identity, i.e., IMPU, User-Name, i.e.,IMPI, Visited-Network-Identifier, i.e., information acquired from theREGISTER message, and User-Authorization-Type, i.e., a userauthorization type, which is valued as REGISTRATION so as to representan initial registration or re-registration. During the interrogation ofthis time, the I-CSCF acquires a “capability set of the S-CSCF forproviding a service for a user” from the HSS, and the capability set isa group of numbers, which identifies the service processing capabilityrequirements on the S-CSCF. The I-CSCF assigns an S-CSCF capable ofsupporting the required relevant service processing to the useraccording to the capability set requirements, and forwards the registerrequest to the assigned S-CSCF (5. REGISTER).

Since it is the initial registration of the user, the S-CSCF needs toperform an authentication on the user. Firstly, the S-CSCF acquires datarequired by the authentication from the HSS (6. MAR˜7. MAA), and thendelivers an authentication challenge to the terminal (8. 401˜10. 401),and the terminal calculates an authentication response and thenre-initiates the registration (11. REGISTER˜12. REGISTER), and theregister request carries the authentication response calculated by theterminal and a duration of a registration cycle expected by theterminal.

The I-CSCF interrogates from the HSS again (13. UAR˜14. UAA), andthrough the interrogation of this time, it acquires an address name ofthe S-CSCF currently performing the authentication on the user. The HSSrecords the address of the S-CSCF of the user when the S-CSCF requeststhe data required by the authentication of the user from the HSS (6.MAR˜7. MAA). After acquiring the address name of the S-CSCF currentlyperforming the authentication on the user, the I-CSCF forwards theregister request carrying the authentication response to the S-CSCF (15.REGISTER). After receiving the register request carrying theauthentication response, the S-CSCF performs a verification on theauthentication response, and if the authentication response issuccessfully verified, the S-CSCF formally records on the HSS that theuser registration is successful, and requests to download subscriptiondata of the user (16. SAR˜17. SAA). The S-CSCF returns a response thatthe register is successful to the user terminal (18. 200 OK˜20. 200 OK).In the 200 OK response, the S-CSCF provides a routing address of theS-CSCF itself in a Service-Route header field, and instructs theterminal to generate a Route header field of a session setup requestmessage by utilizing the routing address in the Service-Route when aservice request is initiated so as to ensure that the service requestcan be routed to the registered S-CSCF for being processed. In addition,the 200 OK response further provides the duration of the registrationcycle determined through a final negotiation.

After the user registration is successful, the situations of recordingthe user registration data by each IMS NE are listed as follows. The HSSrecords the address of the S-CSCF with which the user registers. TheS-CSCF records the subscription service data of the user, the durationof the registration cycle, the address of the P-CSCF where the userpasses through when getting access to the IMS network, and a contactaddress of the user terminal. The P-CSCF records the address (i.e.,Service-Route) of the S-CSCF for providing the service for the user, andthe duration of the registration cycle. The I-CSCF does not record anyuser information.

FIG. 2 is a flow chart of setting up a session between a calling partyand a called party registered in the IMS in the conventional art.

When initiating a session, the calling party determines the Route headerfield in a session setup request according to the Service-Route headerfield acquired during registration. After the session setup request issent to the P-CSCF by the calling party, the P-CSCF routes, according tothe Route header field (1. INVITE˜2. INVITE), the request to the S-CSCFwith which the calling party registers. The S-CSCF routes the requestmessage to the I-CSCF of a home domain of the called user according to adomain identity of the called user (3. INVITE). The called I-CSCFinterrogates from the HSS to acquire, according to an identity of thecalled user (4. LIR˜5. LIA), the address of the S-CSCF with which thecalled user registers, and then forwards the session setup request tothe S-CSCF (6. INVITE). After receiving the session setup request, thecalled S-CSCF updates a target address of the session setup requestINVITE message by utilizing a contact address of the called useraccording to saved local registration data of the called user, andforwards the session setup request to the P-CSCF where the called userpasses through when getting access to the IMS network (7. INVITE). Afterreceiving the session setup request, the called P-CSCF forwards thesession setup request to the called user (8. INVITE), and thus, oneinitial setup process of the end-to-end session in the IMS network isfinished.

If the S-CSCF for providing the service for the user fails, theconventional art adopts a mechanism of using a registration timer totrigger a re-registration so as to assign a new S-CSCF to the user. FIG.3 is a flow chart of triggering re-registration by a registration timerin the conventional art.

After registering with the IMS network successfully, the terminalimmediately starts the registration timer according to the registrationcycle determined through negotiation, and the registration timertriggers the re-registration of the user terminal when the timeoutoccurs. After the terminal initiates the re-registration, the I-CSCF andthe P-CSCF route, according to the records of the initial registrationof the terminal (1. Re-REGISTER˜5. Re-REGISTER), the register request tothe S-CSCF1 with which the terminal registers. If the registered S-CSCF1fails, the I-CSCF cannot receive any response, and as a result, atimeout occurs to a session initiation protocol (SIP) transaction. Sinceit is a re-registration process, the I-CSCF returns 408 Request Timeoutto the terminal (6. 408˜7. 408), and after receiving the response, theterminal immediately initiates an initial registration (8.Ini-REGISTER˜9. Ini-REGISTER). The user has ever registered in the IMSnetwork, so that the register request is still routed to the registeredbut currently failed S-CSCF1, and similarly, the I-CSCF cannot receiveany response, and as a result, the timeout occurs to the SIPtransaction. Since it is the initial registration, the I-CSCF reselectsa new S-CSCF for the user, but firstly it is necessary to acquire theS-CSCF capability set requirements corresponding to the usersubscription information from the HSS (13. UAR˜14. UAA). Then, theI-CSCF reselects an S-CSCF according to the capability set requirements,and forwards the register request to the new S-CSCF (15. REGISTER),thereby the process of reselecting an S-CSCF for the user affected bythe failure is finished. Subsequently, the user finishes registering inthe newly assigned S-CSCF according to the initial registration flow.After the user is successfully registered in the new S-CSCF, the IMSnetwork service of the user restores to a normal status.

As known from the above descriptions about the mechanism of using theregistration timer to trigger the re-registration, if the S-CSCF forproviding the service for the user fails, the network service of theuser cannot be restored until the registration timer of the usertriggers the re-registration and the S-CSCF is reselected. That is tosay, the service interruption duration of the user depends on theduration of the registration cycle of the user. The longer theregistration cycle, the longer is the service interruption duration ofthe user. In order to meet the reliability requirements of thetelecommunication network, the registration cycle is as short aspossible. Unfortunately, if the duration of the registration cycle isset to be too short, it may result in frequent re-registrations. As fora network side, the frequent re-registrations may increase theprocessing burden of the network. Especially for the wireless accessnetwork, the frequent re-registrations excessively occupy the preciousair interface resources. As for a user side, the frequentre-registrations cost the limited energy of a wireless terminal, andthereby shorten a standby time of the terminal.

SUMMARY

Accordingly, the present invention is directed to a method for realizingan IMS disaster tolerance so as to improve the network reliabilitywithout increasing the system burden.

The present invention is further directed to a device for realizing anIMS disaster tolerance so as to improve the network reliability withoutincreasing the system burden.

The detailed technical solution of the present invention is described asfollows.

A method for realizing an IMS disaster tolerance includes the steps asfollows.

An S-CSCF receives a user registration, and backs up necessary datawhich is required when a user service processing is restored on astorage entity in a network.

An I-CSCF of user's home domain receives a service request of a user,and assigns a new S-CSCF to the user and forwards the service request tothe newly assigned S-CSCF, if it is found that the S-CSCF currentlyproviding a service for the user fails.

The newly assigned S-CSCF interrogates and acquires subscription data ofthe user and the necessary data backed up by the original S-CSCF fromthe storage entity, and then restores the user service processingaccording to the subscription data and the backup data.

An I-CSCF further includes a detecting module, an assigning module, anda session setup request processing module.

The detecting module is adapted to judge, according to a receivedsession setup request, whether an S-CSCF with which a user registers andthe S-CSCF currently providing a service for the user fail or not, andinstruct the assigning module to assign a new S-CSCF for the currentuser, if an S-CSCF with which a user registers and the S-CSCF currentlyproviding a service for the user fail; or instruct the session setuprequest processing module to forward the session setup request to theS-CSCF currently providing the service for the user, if an S-CSCF withwhich a user registers and the S-CSCF currently providing a service forthe user do not fail.

The assigning module is adapted to assign the new S-CSCF to the useraccording to an instruction from the detecting module, and instruct thesession setup request processing module to forward the session setuprequest to the newly assigned S-CSCF after finishing assigning the newS-CSCF.

The session setup request processing module is adapted to forward thesession setup request according to an instruction from the detectingmodule or the assigning module.

An S-CSCF further includes a register request processing module, asession setup request processing module, and a user informationprocessing module.

The register request processing module is adapted to send a self addressand an address of an I-CSCF of the current domain to a user when a userregistration is received, store service data of the user in the userinformation processing module, and instruct the user informationprocessing module to back up necessary data which is required when auser service processing is restored on a storage entity in a network.

The session setup request processing module is adapted to process areceived session setup request according to user information.

The user information processing module is connected to the registerrequest processing module and the session setup request processingmodule, and is adapted to store the service data, and interact with thestorage entity in the network so as to back up and acquire the necessarydata which is required when the user service processing is restored.

An HSS includes a user data storing module, adapted to storesubscription data of a user, necessary data which is required when theuser service is restored, and a registered S-CSCF, and further includesan interrogation request processing module. The interrogation requestprocessing module includes an S-CSCF interrogation request determinationsub-module, a disaster tolerance restoring interrogation requestprocessing sub-module, and an unregistered user interrogation requestprocessing sub-module.

The S-CSCF interrogation request determination sub-module is adapted tojudge whether an interrogation request from an S-CSCF is a disastertolerance restoring interrogation request or an unregistered userinterrogation request, and send the request to the disaster tolerancerestoring interrogation request sub-module for being processed if theinterrogation request is a disaster tolerance restoring interrogationrequest; or send the request to the unregistered user interrogationrequest processing sub-module for being processed if the interrogationrequest is an unregistered user interrogation request.

The disaster tolerance restoring interrogation request processingsub-module is adapted to extract, according to the interrogationrequest, corresponding information from the user data storing module andreturn the corresponding information to the S-CSCF.

The unregistered user interrogation request processing sub-module isadapted to judge whether the user is registered or not according to theS-CSCF with which the user registers, and extract the correspondinginformation from the user data storing module and return thecorresponding information to the S-CSCF if the user is not registered;or return an error response to the S-CSCF if the user is registered.

A method for realizing an IMS disaster tolerance includes the steps asfollows.

An S-CSCF receives a user registration, saves service data of a user,and backs up necessary data which is required when a user serviceprocessing is restored on a storage entity in a network.

The S-CSCF receives a service request of the user after the service dataof the user is lost, and then interrogates from the storage entity andacquires subscription data of the user and the necessary data backed-upin the storage entity, and processes the service request of the useraccording to the subscription data and the necessary data.

It can be seen from the above description that, in the presentinvention, the I-CSCF of the user home domain detects a workingsituation of the S-CSCF with which the user registers. When a callingparty initiates a session, a session setup request of the calling partyis firstly routed by a calling P-CSCF to an I-CSCF of the calling homedomain, and then routed by the I-CSCF of the calling home domain to anS-CSCF with which the calling party registers. During the session setupprocess, the I-CSCF of the calling home domain may find that the S-CSCFwith which the calling party registers fails, and then immediatelyassigns a new S-CSCF to the calling party, and meanwhile, the I-CSCF ofthe called home domain may find that the S-CSCF with which the calledparty registers fails, and then immediately assigns a new S-CSCF to thecalled party. That is to say, once the S-CSCF fails, the influenced userrestores the service when a call is established without waiting for are-registration timer of a user terminal to trigger a re-registration torestore the network service so as to improve the network reliabilitywithout increasing the system burden.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart when a user intending to get access to an IMSnetwork subscribes to and registers with the IMS network;

FIG. 2 is a flow chart of setting up a session between a calling partyand a called party that register with the IM;

FIG. 3 is a flow chart of triggering a re-registration by a registrationtimer;

FIG. 4 is an overall flow chart of the present invention;

FIG. 5 is a flow chart of a user registration according to an embodimentof the present invention;

FIG. 6 is a flow chart when a calling party initiates a call for a firsttime after an S-CSCF with which the calling party registers failsaccording to an embodiment of the present invention, including FIGS. 6a, 6 b, 6 c, and 6 d;

FIG. 7 is a flow chart when a call setup is performed on a called partyfor a first time after an S-CSCF with which the called party registersfails according to an embodiment of the present invention, includingFIGS. 7 a, 7 b, 7 c, and 7 d;

FIG. 8 is a flow chart when the calling party initiates a subsequentcall after the S-CSCF with which the calling party registers failsaccording to an embodiment of the present invention;

FIG. 9 is a flow chart when a subsequent call setup is performed on thecalled party after the S-CSCF with which the called party registersfails according to an embodiment of the present invention;

FIG. 10 is a flow chart of a re-registration performed before a disastertolerance is restored according to an embodiment of the presentinvention;

FIG. 11 is a flow chart of a re-registration performed after a disastertolerance is restored according to an embodiment of the presentinvention;

FIG. 12 is a block diagram of an I-CSCF according to an embodiment ofthe present invention;

FIG. 13 is a block diagram of an S-CSCF according to an embodiment ofthe present invention; and

FIG. 14 is a block diagram of an HSS according to an embodiment of thepresent invention.

DETAILED DESCRIPTION

A core concept of the present invention lies in that, when a userregisters with an S-CSCF, necessary data used in a restoring process isbacked up on a storage entity in a network; for example, an HSS. Duringa session setup process, if an I-CSCF of the user's home domain detectsthat the S-CSCF with which the user registers fail, the I-CSCF assigns anew S-CSCF to the user; and the newly assigned S-CSCF acquires thebackup data and subscription data of the user from the storage entity inthe network, and then restores the user service processing.

In order to make the objectives, technical solutions, and efficacies ofthe present invention more comprehensible, a detailed description isgiven below with reference to the embodiments and accompanying drawings.

FIG. 4 is an overall flow chart of the present invention.

In Step 401, when an S-CSCF receives a user registration, the S-CSCFbacks up necessary data which is required when a user service processingis restored on an HSS.

Here, the S-CSCF backs up the data on the HSS through a transmission ofa new information cell, that is, AVP User-Backup-Data, defined in anembodiment of the present invention. The backup data is saved in the HSSby taking one user as a unit, and when the disaster tolerance restoringis required to perform, the newly assigned S-CSCF may acquire the backupdata of the user from the HSS.

In Step 402, an I-CSCF of the user's home domain receives a servicerequest of the user, and assigns a new S-CSCF to the user if it is foundthat the S-CSCF with which the user registers fails.

By inspecting the status of the S-CSCF currently providing the servicefor the user, the I-CSCF determines that the S-CSCF currently providingthe service for the user fails according to an inspection result.Alternatively, the I-CSCF may directly forward the service request tothe S-CSCF, and determines that the S-CSCF currently providing theservice for the user fails when no response is received from the S-CSCFafter a certain time period elapsed.

Two manners for the I-CSCF to assign the new S-CSCF are provided in theembodiment of the present invention.

In manner A, the I-CSCF interrogates a capability requirement on theS-CSCF in the subscription data of the user from the HSS of the userhome domain, and assigns the new S-CSCF according to the capabilityrequirement on the S-CSCF of the user.

In manner B, the I-CSCF statically configures a local redundancyrelation among S-CSCFs, selects the S-CSCF having a redundancy relationwith the failed S-CSCF from a local redundancy relation table, andassigns the selected S-CSCF to the user.

In Step 403, the newly assigned S-CSCF acquires the data backed up bythe original S-CSCF from the HSS of the user home domain, and thenrestores the user service processing according to the data.

The above steps are described in detail as follows.

FIG. 5 is a flow chart of a user registration according to an embodimentof the present invention.

In FIG. 5, once a user equipment (UE) initiates a registration and issuccessfully authenticated (1. REGISTER˜15. REGISTER), the S-CSCF needsto request to download the subscription data of the user from the HSS(16. SAR). In order to back up the necessary data which is required whenthe user service processing is restored on the HSS, an AVP with anextended definition needs to be added in the SAR message, that is, AVPUser-Backup-Data, and the AVP at least includes the followinginformation:

-   -   A SIP URL of the P-CSCF through which the path of the user        registration passes is adapted to address the P-CSCF when a        called service is restored; and    -   A contact address of the user registration is adapted to address        the user terminal when the called service is restored.

The HSS saves the AVP User-Backup-Data according to each user, but it isnot necessary to resolve the content of the AVP, that is to say, thecontent of the AVP is transparent for the HSS.

After successfully acquiring the user data (17. SAA), the S-CSCF returnsa register success message (18. 200 OK) to the I-CSCF. In the 200 OKmessage, Service-Route determined by the S-CSCF includes not only arouting address of the S-CSCF itself, but also a routing address of theI-CSCF of the current domain added before the routing address of theS-CSCF itself. In addition, a calling tag needs to be added in therouting address of the I-CSCF in the Service-Route, for example, theuser part of the SIP URL address is set as “orig.” The I-CSCF forwardsthe register success message to the P-CSCF, and then the P-CSCF forwardsthe register success message to the UE (19. 200 OK˜20. 200 OK).

Thus, when a calling party initiates a session, a Route header field ina session setup request INVITE message is determined according to theService-Route header field of the 200 OK message received duringregistration, that is, the first one in the Route header field is theI-CSCF address in the current domain, and the second one is the S-CSCFaddress. Therefore, the session setup request is firstly forwarded fromthe P-CSCF to I-CSCF, processed by the I-CSCF, and then routed to theS-CSCF for being processed, instead of being directly routed from theP-CSCF to the S-CSCF for being processed. After receiving the sessionsetup request, the I-CSCF determines that a direction of the currentsession setup request is from a user to a network according to thecalling tag.

After the user is registered in the S-CSCF, if the S-CSCF fails,different processing flows are adopted in the present inventiondepending upon the factors that whether the failed S-CSCF is the S-CSCFwith which the calling party or the called party registers, and whetherthe current session is the first session after the failure or not.

FIG. 6 is flow chart when a calling party initiates a call for a firsttime after an S-CSCF with which the calling party registers failsaccording to an embodiment of the present invention.

After the S-CSCF fails, if a user originally registered with the S-CSCFinitiates a session setup request for the first time before triggering are-registration, the session setup request is forwarded to the I-CSCF ofthe user home domain by the P-CSCF of the user home domain. After theI-CSCF finds that a certain S-CSCF fails, according to the manner A inStep 402, the I-CSCF interrogates the capability requirement on theS-CSCF of the user during the user subscription form the HSS, andimmediately assigns a new S-CSCF to the user; or according to the mannerB in Step 402, the I-CSCF needs to configure a local S-CSCF redundancyrelation table, and selects a new S-CSCF from the table. No matter whichone of the above two manners is used, after finishing assigning theS-CSCF, the I-CSCF adds a disaster tolerance restoring indicatorparameter in a session setup request to be forwarded to the newlyassigned S-CSCF. After receiving the session setup request, the newlyassigned S-CSCF determines that the call is a disaster tolerancerestoring call according to the disaster tolerance restoring indicator,and interrogates and acquires the backup data and the subscription dataof the user from the HSS so as to provide the service for the user.

In FIG. 6, after receiving the session setup request from the user, theP-CSCF routes the call to the I-CSCF according to the Service-Route (1.INVITE˜2. INVITE). The I-CSCF can detect a network failure of the S-CSCFin the current domain, and after receiving the session setup request ofthe user, the I-CSCF determines that the received request is a callingrequest sent from a user side to a network side and a next hop is anS-CSCF NE according to the topmost address of the Route header field inthe received INVITE message, that is, an address pointed to the I-CSCFitself, and the included “orig” sign.

The I-CSCF judges whether the S-CSCF currently with which the userregisters fails or not according to a next address in the Route headerfield of the INVITE message, and starts to assign the new S-CSCF to theuser after finding that the next hop, i.e., the S-CSCF, fails.

In FIG. 6 a, the I-CSCF assigns the new S-CSCF to the user by adoptingthe manner A of Step 402.

The I-CSCF interrogates and acquires the address of the S-CSCF withwhich the calling user currently registers and the capabilityrequirement on the S-CSCF for providing a service for the calling userfrom the HSS (3. UIR/UAR/LIR˜4. UIA/UAA/LIA), which may be processedthrough newly added interface messages UIR/UIA, and may be processed ina manner of extending the existing interface messages UAR/UAA orLIR/LIA.

In manner 1, the newly added interface messages UIR/UIA are adopted.

UIR is a user information request.

UIA is a user information answer.

The UIR must carry only one AVP, and the AVP is an AVP Public-Identity,which is valued as an IP multimedia public identity (IMPU) of thecalling user.

A message structure of the UIA is shown as follows.

Name of Information Corresponding Element Diameter AVP Type DescriptionResult Result-Code/ Mandatory Operation result. Experimental- As for thevalue definition, Result please refer to Diameter protocol or 3GPPprotocol. S-CSCF Server- Optional It indicates the capabilitycapabilities Capabilities requirement of the S-CSCF assigned to theuser. If the message does not carry the AVP, it represents that theI-CSCF can randomly assign any S-CSCF. S-CSCF Server-Name Condition Ifthe user is registered, Name optional the AVP shall exist, which isvalued as an address/name of the S-CSCF with which the user currentlyregisters.

In manner 2, the structure definition of the extended existing interfacemessages UAR/UAA and relevant processing thereof are adopted.

UAR is a user authorization request.

UAA is a user authorization answer.

The UAR message structure defined by the existing protocol is modifiedas follows: (1) A value of “RESTORE” is added for the AVPUser-Authorization-Type, which is applied to a scenario of the presentinvention; (2) the type of the AVP User-Name is changed from mandatoryto optional, and when the value of the AVP User-Authorization-Type isRESTORE, the AVP may not need to be carried; and (3) the type of the AVPVisited-Network-Identifier is changed from mandatory to optional, andwhen the value of the AVP User-Authorization-Type is RESTORE, the AVPmay not need to be carried.

After the HSS receives the UAR with the value of the AVPUser-Authorization-Type as RESTORE, the content of the returned UAAmessage is required to be the same as that of the UIA message, and thestructure definition of the UAA message is not modified in theembodiment of the present invention. That is to say, the structure ofthe UIA message in the embodiment of the present invention is the sameas that of the UAA message in the conventional art, but merely the namesof the messages are different. The UAA message in the embodiment of thepresent invention may adopt the definition of the UAA message in theconventional art.

In manner 3, the structure definition of the extended existing interfacemessages LIR/LIA and relevant processing thereof are adopted.

LIR is a location information request.

LIA is a location information answer.

One parameter is newly added to the LIR, and the parameter requires thatthe HSS carries a capability set of the S-CSCF when the HSS returns theLIA message. Once receiving the LIR message carrying the newly addedparameter, the HSS carries the requested capability set in the returnedLIA message. The present invention may adopt the LIA message definitionin the conventional art.

After acquiring the name of the S-CSCF currently providing the servicefor the user and the capability requirement on the S-CSCF of the userduring the subscription according to any of the above manners, theI-CSCF judges whether the S-CSCF currently providing the service for theuser fails or not, and if yes, the I-CSCF assigns a new S-CSCF to theuser according to the capability requirement data on the S-CSCF.

In FIG. 6 b, the I-CSCF assigns the new S-CSCF for the user by adoptingthe manner B in Step 402.

The I-CSCF needs to configure a local static data table, that is, anS-CSCF redundancy relation table so as to record redundancy relationsamong the S-CSCFs in the current domain. Particularly, in the currentdomain, according to the capabilities, the S-CSCFs are divided intodifferent groups, that is, S-CSCF redundancy relation groups, andS-CSCFs in the same group have the same capability and have a redundancyrelation corresponding to each other.

The I-CSCF firstly interrogates and acquires the address of the S-CSCFcurrently providing the service for the calling user from the HSS byutilizing the IMPU of the calling user (3. LIR˜4. LIA). It should benoted that, in the present invention, it is the I-CSCF of the callinguser home domain that calls the LIR/LIA, which aims at interrogating andacquiring the address of the S-CSCF currently providing the service forthe calling user. After interrogating the S-CSCF currently providing theservice for the user, the I-CSCF further determines the status of theS-CSCF, and if the S-CSCF is in a failed status, the I-CSCF looks up theS-CSCF redundancy relation table, finds out the S-CSCF redundancyrelation group where the S-CSCF belongs to, and selects one S-CSCFthere-from for being assigned to the user, which serves as the newS-CSCF for providing the service to the user.

Regardless of manner A or manner B, after finishing assigning the newS-CSCF, the I-CSCF forwards the session setup request to the newlyassigned S-CSCF (5. INVITE). In the request message, the I-CSCF needs toadd one disaster tolerance restoring indicator parameter “tag=restore”,which represents that the session setup request is a disaster tolerancerestoring session setup request, and the S-CSCF that receives suchrequest needs to perform a restoring process.

After receiving the disaster tolerance restoring session setup requestand determining that the local data of the calling user does not exist,the S-CSCF further judges whether the request carries the disastertolerance restoring indicator or not. If it is determined that thesession setup request is a disaster tolerance restoring session setuprequest according to the disaster tolerance restoring indicator carriedin the request, the newly assigned S-CSCF interrogates and acquires thebackup information and the subscription data of the user from the HSSthrough a disaster tolerance restoring interrogating message (6.SRR/SAR˜7. SRA/SAA), and the above process is achieved through thefollowing two detailed manners.

In manner 1, newly added interface messages SRR/SRA are adopted.

SRR is a service restore request, and a message structure of the SRR isshown as follows.

Name of Information Corresponding Element Diameter AVP Type DescriptionPublic User Public-Identity Mandatory User public identity to beIdentity interrogated S-CSCF Server-Name Mandatory Address name of theS-CSCF Name initiating the request

SRA is a service restore answer, and a message structure of the SRA isshown as follows.

Name of Information Corresponding Element Diameter AVP Type DescriptionPublic User Public-Identity Mandatory Received user public Identityidentity Registration Result-Code/ Mandatory Restore operation resultExperimental- result, and as for the Result value definition, pleaserefer to Diameter protocol and 3GPP relevant protocol. User ProfileUser-Data Condition If the status of the user optional in the HSS isregistered in the received request message, the AVP should exist in themessage, which is valued as the subscription data of the user.Associated- Associated- Condition If the registration status Back InfoBack Info optional of the user in the HSS is registered, the AVP shouldexist, which is valued as the data backed up by the original S-CSCFduring the user registration.

Associated-Back Info is a composite AVP, and the structure definitionthereof is listed as follows.

Associated-Back Info::= < AVP header: TBD > * { User-Name } * {Charging-Information} * { User-Backup-Data }

That is to say, when the newly assigned S-CSCF interrogates the userdata backed up on the HSS by the failed S-CSCF from the HSS, the HSSsends the backup information to the newly assigned S-CSCF via the AVPUser-Backup-Data nested in the AVP Associated-Back Info of the SRAmessage. According to the above registration flow, the AVPUser-Backup-Data is sent to the HSS by the failed S-CSCF through the SARmessage when the user registers in the failed S-CSCF, and is saved bythe HSS.

In manner 2, the structure definition of the SAR/SAA in the existingprotocol is modified.

SAR is a server assignment request.

SAA is a server assignment answer.

In the present invention, the SAR message is modified as follows: (1) avalue of “RESTORE” of the AVP Server-Assignment-Type is added, which isapplied to the present invention; and (2) when the value of the AVPServer-Assignment-Type is RESTORE, the AVP Public-Identity must exist,which is valued as the IMPU of a disaster tolerance restoring user.

In the present invention, the SAA message is modified as follows: (1)the AVP Public-Identity must be included, which is valued as the IMPU inthe request message; and (2) if the registration status of the user inthe HSS is registered, the AVP Associated-Back-Info should carry thebackup data during the user registration.

Regardless of any of the above manners, in the embodiment of the presentinvention, the newly assigned S-CSCF needs to add a disaster tolerancerestoring indicator parameter in the AVP Server Name of the SRR/SARmessage. The HSS replaces the address of the S-CSCF for providing theservice for the user and currently recorded by the HSS with the AVPServer Name carrying the disaster tolerance restoring indicatorparameter. Meanwhile, the newly assigned S-CSCF tags the user as adisaster tolerance restoring user, and the disaster tolerance restoringuser does not formally register with this S-CSCF.

After acquiring the restoring data of the disaster tolerance restoringuser through any of the above manners, the S-CSCF restores the servicedata of the user, and restores a session processing of the user.

It should be noted that, the user is not registered in the newlyassigned S-CSCF currently. After the S-CSCF has successfully restoredthe service of the user, it further needs to start a disaster tolerancerestoring timer for the user, and a timeout duration thereof may be setdepending upon the actual requirements. If the user does not initiate aregistration flow before the timeout of the disaster tolerance restoringtimer, the newly assigned S-CSCF deletes the data of the user, that is,to perform a network deregistration on the user. Once being started, thedisaster tolerance restoring timer is not stopped or reset though theuser performs a subsequent session. Once the user initiates are-registration, the disaster tolerance restoring timer is terminated,and then the subsequent process is performed according to the initialregistration flow provided by the present invention. The situation isdescribed in detail as follows.

In addition, as described above, after receiving the session setuprequest, the S-CSCF firstly judges whether the local data of the callinguser exists or not, and if the local data of the calling user exists,the call is continued according to a normal flow. Otherwise, the S-CSCFfurther judges whether the session setup request carries the disastertolerance restoring indicator or not. If the session setup requestcarries the disaster tolerance restoring indicator, the S-CSCFinterrogates and acquires the backup information and the subscriptiondata of the user from the HSS according to the disaster tolerancerestoring flow (6. SRR/SAR˜7. SRA/SAA).

However, another situation still exists in the practical work, that is,the S-CSCF first fails and then restores from a failed status, but theservice data recorded by the S-CSCF is lost. FIGS. 6 c and 6 d show theprocessing flows under such situation. Since the S-CSCF restores fromthe failure, when the calling party initiates a call, the I-CSCFconsiders that the S-CSCF works normally so as to directly forward thesession setup request without carrying a disaster tolerance restoringindicator parameter to the S-CSCF (3. INVITE).

In this case, although the S-CSCF determines that the local data of thecalling user does not exist, the call request does not carry a disastertolerance restoring indicator as well, and thus, the S-CSCF does notconsider that the session setup request is a disaster tolerancerestoring session setup request, but considers that the terminal thatsends the session setup request is not registered yet. Therefore, theS-CSCF requests the user data from the HSS through an unregistered userinterrogating message (4. SAR (UNREGISTERED_USER)).

In FIG. 6 c, in the records of the HSS, the calling user is registeredin the S-CSCF. Thus, after receiving the interrogation request from theS-CSCF, the HSS finds that the interrogated user is currently in the“registered” status, and determines that an error occurs to theinterrogation type of the S-CSCF so as to return an error response (4.SAA (DIAMETER_ERROR_IN_ASSIGNMENT_TYPE)). After receiving the errorresponse, the S-CSCF judges whether itself restores from the failure ornot, and if yes, the S-CSCF initiates a disaster tolerance restoringflow, and interrogates and acquires the backup information and thesubscription data of the user from the HSS (6. SRR/SAR˜7. SRA/SAA) so asto restore the service for the calling user. It should be noted that,the AVP Server in the SRR/SAR messages (6. SRR/SAR˜7. SRA/SAA) issimilar to the corresponding message in FIGS. 6 a and 6 b, so it is notrepeatedly described here.

In FIG. 6 d, in the records of the HSS, the calling user is registeredin the S-CSCF. Thus, after receiving the interrogation request from theS-CSCF, the HSS finds that the interrogated user is currently in the“registered” status, and determines that an error occurs to theinterrogation type of the S-CSCF. Different from FIG. 6 c, when the HSSreturns an error response to the S-CSCF according to FIG. 6 d, the HSSsends the backup information and the subscription data of the user tothe S-CSCF (4. SAA (DIAMETER_ERROR_IN_ASSIGNMENT_TYPE, User Data, BackupData)). After receiving the error response, the S-CSCF directly acquiresthe backup information and the subscription data of the user from theerror response so as to restore the service for the calling user.

FIG. 7 a is a flow chart when a call setup is performed on a calledparty for a first time after an S-CSCF with which the called partyregisters fails according to an embodiment of the present invention.

After an S-CSCF1 fails, if a user registered in the S-CSCF1 serves as acalled party, an I-CSCF of the current domain firstly receives a sessionsetup request from a calling side (1. INVITE). The I-CSCF interrogatesand acquires an address name of the S-CSCF with which the called userregisters from the HSS, that is, the S-CSCF1, (2. LIR˜3. LIA), and thenthe I-CSCF determines that the S-CSCF1 fails, so that the I-CSCF needsto assign a new S-CSCF to the user. Similarly, the new S-CSCF isassigned to the user according to the manner A and the manner B in Step402. According to the manner A, the I-CSCF interrogates the capabilityrequirement on the S-CSCF of the called user during the subscriptionfrom the HSS (4. UIR/UAR/LIR˜5. UIA/UAA/LIA). Definitely, the UAR/UAA orLIR/LIA needs to be extended, the specific extending manner thereof isthe same as that described above, so it is not repeatedly describedhere. The I-CSCF assigns a new S-CSCF to the user according to theacquired capability requirement on the S-CSCF. According to the mannerB, the I-CSCF acquires the new S-CSCF from a local configuration,without interrogating and acquiring the capability requirement on theS-CSCF from the HSS, and the detailed process thereof is the same asthat described above, so it is not repeatedly described here. That is tosay, in FIG. 7 a, 4. UIR/UAR/LIR˜5. UIA/UAA/LIA are optional steps.

Supposing the I-CSCF assigns a new S-CSCF2 to the called user, theI-CSCF forwards a called request to the S-CSCF2 (6. INVITE), and adds adisaster tolerance restoring indicator parameter to the request. Afterreceiving the session setup request, the S-CSCF2 determines that therequest is a disaster tolerance restoring session setup requestaccording to the disaster tolerance restoring indicator parameter, andinterrogates and acquires the subscription data and the backup data ofthe called user from the HSS (7. SRR/SAR˜8. SRA/SAA), and the detailedmessage content structure is the same as that described in 6. SRR/SAR˜7.SRA/SAA in FIGS. 6 a and 6 b, which thus is not repeatedly describedhere. After acquiring the subscription data and the backup data of theuser, the S-CSCF2 restores the registration record of the called user,and forwards, according to the P-CSCF address and the contact address ofthe user provided in the backup data (9. INVITE), the session setuprequest to the P-CSCF with which the called user registers. Then, thesession is continued. Similarly, the newly assigned S-CSCF also tags theuser as a disaster tolerance restoring user, and the disaster tolerancerestoring user does not formally registers with this S-CSCF. The newlyassigned S-CSCF needs to start a disaster tolerance restoring timer.

In addition, similarly, as for an S-CSCF with which the called userregisters, the S-CSCF may first fail and then restore from the failedstatus, but the service data is lost. FIGS. 7 b and 7 c respectivelyshow a processing flow under such a situation. In this case, afterinterrogating and acquiring an address name of the S-CSCF with which thecalled user from the HSS registers (2. LIR˜3. LIA), the I-CSCF findsthat the S-CSCF with which the called user working normally registers soas to directly forward a session setup request without carrying adisaster tolerance restoring indicator parameter to the S-CSCF withwhich the called user registers (4. INVITE). Then, the S-CSCF with whichthe called party registers and the processing flow of the HSS aresimilar to the S-CSCF and the processing flow of the HSS described inFIGS. 6 c and 6 d, which thus are not repeatedly described here.

In the above embodiments, when the S-CSCF with which the calling partyregisters fails and when the S-CSCF with which the called partyregisters fails, the call setup flows adopted by the present inventionhave been respectively described. In FIGS. 6 and 7, the call setup isperformed for the first time after the S-CSCF fails. If after the S-CSCFfails, the call setup is performed for at least once according to theflow of FIG. 6 or 7, the flow adopted in a subsequent call setup isdifferent from that of FIG. 6 or 7, and the detailed descriptionsthereof are listed as follows.

FIG. 8 is a flow chart when the calling party initiates a subsequentcall after the S-CSCF with which the calling party registers failsaccording to an embodiment of the present invention.

After the S-CSCF1 fails, if the user originally registered in theS-CSCF1 has ever performed a session before a re-registration, theI-CSCF of the user home domain assigns a new S-CSCF for the useraccording to the flow of FIG. 6, which is assumed to be the S-CSCF2.

If the user initiates a session again before the re-registration, theP-CSCF still routes the session to the I-CSCF according to the localService-Route recorded during the user registration (1. INVITE˜2.INVITE). After receiving the session setup request, the I-CSCFdetermines that the session is a calling motion, and the type of thenext hop NE is the S-CSCF, so that the I-CSCF inspects a status of thenext hop NE, and finds that the S-CSCF1 is in the failed status. Thus,the I-CSCF interrogates and acquires the address of the S-CSCF withwhich the calling user from the HSS (3. UIR/UAR/LIR˜4. UIA/UAA/LIA)currently registers, and the detailed interrogation manner and themessage content structure are the same as that described in FIG. 6,which thus are not repeatedly described here. As described above, theaddress of the S-CSCF currently providing the service for the userrecorded by the HSS carries a disaster tolerance restoring indicator, sothat the address of the S-CSCF2 returned by the HSS to the I-CSCFcarries the disaster tolerance restoring indicator.

The I-CSCF interrogates and acquires that the S-CSCF with which thecalling user currently registers is the S-CSCF2, and the I-CSCFdetermines that the S-CSCF2 is in a normal service status so as toforward the session setup request to the S-CSCF2 (5. INVITE), and carrythe disaster tolerance restoring indicator parameter in the request.

After the S-CSCF2 receives the session setup request, since the callinguser has performed the disaster tolerance restoring before, the S-CSCF2has acquired the service data of the user, and thus, the S-CSCF2 candirectly provide the service for the user, without interrogating theuser data from the HSS.

FIG. 9 is a flow chart when a subsequent call setup is performed on thecalled party after the S-CSCF with which the called party registersfails according to an embodiment of the present invention.

After the S-CSCF1 fails, if a user originally registering with theS-CSCF1 has ever performed a session before a re-registration, an I-CSCFof the user home domain assigns a new S-CSCF for the user according tothe flow in FIG. 7, which is assumed to be the S-CSCF2.

If the user serving as a called party performs a subsequent sessionbefore the re-registration, the network processing flow is similar tothat in the conventional art, but the difference there-between lies inthat, after interrogating and acquiring the address of the S-CSCF withwhich the user currently registers, i.e., the S-CSCF2, from the HSS (2.LIR-3.LIA), the I-CSCF can determine that the S-CSCF2 currentlyproviding the service for the user is the S-CSCF selected in thedisaster tolerance restoring flow according to the disaster tolerancerestoring indicator parameter in the S-CSCF2 address in this embodiment.Thus, when the I-CSCF forwards the session setup request to the S-CSCF2,the I-CSCF adds the disaster tolerance restoring indicator parameter inthe request message. After the S-CSCF2 receives the session setuprequest, since the called user has performed the disaster tolerancerestoring before, the S-CSCF2 has acquired the service data of the user,and thus, the S-CSCF2 can directly provide the service for the userwithout interrogating the user data from the HSS.

According to the conventional art, once the S-CSCF with which the userregisters fails, a re-registration flow is required definitely.According to the embodiments of the present invention, before there-registration, the user may already setup a call, and restore the userservice processing by using the new S-CSCF according to the flows ofFIGS. 6 to 9. Definitely, it may be possible that the user is notregistered in a new S-CSCF before the re-registration. The registrationflow adopted by the embodiment of the present invention is differentfrom the conventional art, and thus, under the two situations, there-registration flow adopted by the embodiment of the present inventionis also different from that in the conventional art.

FIG. 10 is a flow chart of a re-registration performed before a disastertolerance is restored according to an embodiment of the presentinvention.

In FIG. 10, after the S-CSCF1 fails, if a user originally registeringwith the S-CSCF1 does not perform the disaster tolerance restoringprocess, a registration timer initiates a re-registration when a timeoutoccurs, so that the I-CSCF interrogates and acquires the address name ofthe S-CSCF currently providing the service for the user from the HSS (3.UAR˜4. UAA). According to an interrogation result, the I-CSCF determinesthat the S-CSCF1 currently providing the service for the user is in afailed status, the I-CSCF does not forward the register request to thefailed S-CSCF as in the conventional art, but directly interrogates thecapability requirement on the S-CSCF of the user during the subscriptionfrom the HSS (5. UAR˜6.UAA), and immediately assigns a new S-CSCF forthe user according to the capability requirement in the embodiment ofthe present invention. Then, the I-CSCF forwards the register request tothe newly assigned S-CSCF (7. REGISTER). After the newly assigned S-CSCFreceives the register request, the subsequent processing steps (8.MAR˜22. 200 OK) are the same as the corresponding steps (6. MAR˜20. 200OK) in the initial registration flow adopted by the embodiment of thepresent invention in FIG. 5, which thus are not repeatedly describedhere.

FIG. 11 is a flow chart of a re-registration performed after a disastertolerance is restored according to an embodiment of the presentinvention.

After the S-CSCF1 fails, if the user originally registered in theS-CSCF1 has performed the disaster tolerance restoring process beforethe re-registration, as mentioned above, the newly assigned S-CSCFprovides the service for the user, but the user does not formallyregisters with the newly assigned S-CSCF.

When the user initiates a re-registration because the registration timertimes out, the register request is forwarded to the I-CSCF of the userhome domain (1. REGISTER˜2. REGISTER). The I-CSCF interrogates theS-CSCF currently providing the service for the user from the HSS, andthe HSS sends the S-CSCF2 address with the disaster tolerance restoringtag to the I-CSCF (3. UAR˜4. UAA). Then, the I-CSCF forwards theregister request to the S-CSCF2 according to the address.

Since the user currently applying for a registration is a disastertolerance restoring user, the S-CSCF2 may be set to perform anauthentication on the user according to the disaster tolerance restoringtag carried in the register request (6. MAR˜15. REGISTER), anddefinitely, the authentication step may be omitted. After theauthentication is successfully passed, the S-CSCF2 formally records thatthe user registration is successful to the HSS (16. SAR˜17. SAA), and nodisaster tolerance restoring indicator is carried during the aboverecording process. Furthermore, the HSS needs to update the S-CSCF2address with the disaster tolerance restoring indicator originallyrecorded by the HSS with the S-CSCF2 address without the disastertolerance restoring indicator. Meanwhile, the newly assigned S-CSCF alsotags the user as a formally registered user.

The subsequent steps are the same as the corresponding steps (18. 200OK˜20. 200 OK) in the initial registration flow of the present inventionin FIG. 5, which thus are not repeatedly described here.

If the S-CSCF restores from the failed status, and during the period ofrestoring from the failed status, no re-registration due to the timeoutof the registration timer is triggered, and no disaster tolerancerestoring flow is triggered due to a relevant session setup request, thepossible scenarios under such situations include, for example, theS-CSCF is reset/restarted, and a communication network of the S-CSCFfails and then restores to a normal status and the like.

In this case, when the I-CSCF detects that the S-CSCF fails, the I-CSCFstarts an acknowledgement timer for the failed S-CSCF, and determinesthat a duration of the acknowledgement timer is a maximum registrationcycle in the current domain.

After a certain failed S-CSCF restores to a normal status, if the I-CSCFreceives a session setup request sent to the S-CSCF, the I-CSCF forwardsthe session setup request to the S-CSCF. If the acknowledgement timerstarted for the S-CSCF does not time out, the I-CSCF must add a disastertolerance restoring indicator parameter when the I-CSCF forwards thesession setup request to the S-CSCF. If the acknowledgement timer timesout, it represents that all the users with the service provided by theS-CSCF have performed the re-registration for at least once, so that nodisaster tolerance restoring indicator parameter is added.

After the S-CSCF receives the session setup request, if it is found thatthe relevant user is not registered to this S-CSCF, under the situationthat the request carries the disaster tolerance restoring indicatorparameter, the S-CSCF performs the relevant processing according to theflow of the present invention. On the contrary, if the request does notcarry the disaster tolerance restore indicator parameter, the S-CSCFperforms the relevant processing according to the conventional art.

In order to realize the above methods of the present invention, it isneeded to correspondingly extend the structures and functions of theexisting I-CSCF, S-CSCF, and HSS.

FIG. 12 is a block diagram of an I-CSCF according to an embodiment ofthe present invention.

In an I-CSCF provided according to the present invention, three modulesare increased or modified on the basis of the existing I-CSCF, includinga detecting module, an assigning module, and a session setup requestprocessing module.

The detecting module is connected to the assigning module and thesession setup request processing module, and is adapted to judge,according to a received session setup request, whether an S-CSCF withwhich a user registers and an S-CSCF currently providing a service forthe user fails or not, and if yes, the detecting module instructs theassigning module to assign a new S-CSCF to the current user. Otherwise,the detecting module instructs the session setup request processingmodule to forward the session setup request.

In order to judge whether the S-CSCF fails or not, the detecting moduleneeds to firstly acquire an S-CSCF address. Therefore, the detectingmodule further includes an address acquiring sub-module, adapted toacquire the S-CSCF address. The address acquiring sub-module resolves aRoute header field in the session setup request to acquire the S-CSCFaddress, or interrogates and acquires the address of the S-CSCFcurrently providing the service for the user from the HSS according tothe user identity in the session setup request.

The assigning module is connected to the detecting module and thesession setup request processing module, and is adapted to assign thenew S-CSCF to the user according to an instruction from the detectingmodule, and instruct the session setup request processing module toforward the session setup request after finishing assigning the newS-CSCF.

The assigning module may include any one of an interrogating sub-moduleand a redundancy relation storing sub-module. The interrogatingsub-module is adapted to interrogate a capability requirement on anS-CSCF in subscription data of the user from the HSS, and assign theS-CSCF to the user according to the capability requirement. Theredundancy relation storing sub-module is adapted to store S-CSCFredundancy relation groups, select one S-CSCF from a correspondingredundancy relation group according to the address of the S-CSCFcurrently providing the service for the user, and assign the S-CSCF tothe user.

The session setup request processing module is connected to thedetecting module and the assigning module, and is adapted to forward thesession setup request according to an instruction from the detectingmodule or the assigning module. If the session setup request isforwarded according to an instruction from the detecting module, thereceived session setup request is directly forwarded. If the sessionsetup request is forwarded according to an instruction from theassigning module, a disaster tolerance restoring indicator is carried inthe session setup request. The operation of judging whether theinstruction is sent from the detecting module or the assigning modulemay be finished by an instruction determination sub-module in thesession setup request processing module.

FIG. 13 is a block diagram of an S-CSCF according to an embodiment ofthe present invention.

In an S-CSCF provided according to an embodiment of the presentinvention, four modules are increased or modified on the basis of theexisting S-CSCF, including a register request processing module, asession setup request processing module, a user information processingmodule, and a disaster tolerance restoring timer.

The register request processing module is connected to the userinformation processing module, and is adapted to receive a userregistration, send a self address and an address of an I-CSCF of thecurrent domain to the user, store service data of the user in the userinformation processing module, and instruct the user informationprocessing module to back up necessary data which is required when auser service processing is restored on a storage entity in a network.

The session setup request processing module is connected to the userinformation processing module, and is adapted to process a receivedsession setup request according to user information.

Particularly, the session setup request processing module includes aservice data interrogating sub-module, a disaster tolerance restoringindicator interrogating sub-module, and a session setup requestforwarding sub-module.

The service data interrogating sub-module is adapted to interrogatewhether the user information processing module has service data or not,and if yes, the service data interrogating sub-module sends the sessionsetup request to the session setup request forwarding sub-module.Otherwise, the service data interrogating sub-module sends the sessionsetup request to the disaster tolerance restoring indicatorinterrogating sub-module.

The session setup request forwarding sub-module is adapted to forwardthe session setup request according to the service data.

The disaster tolerance restoring indicator interrogating sub-modulejudges whether the session setup request carries a disaster tolerancerestoring indicator or not, and if yes, the disaster tolerance restoringindicator interrogating sub-module instructs the user informationprocessing module to send a disaster tolerance restoring interrogationrequest to the storage entity in the network and acquires the servicedata. Otherwise, the disaster tolerance restoring indicatorinterrogating sub-module instructs the user information processingmodule to send an unregistered user interrogation request to the storageentity in the network and acquires the service data.

The error response processing sub-module is adapted to judge whether anerror response includes the service data or not after receiving theerror response from the storage entity in the network, in which when theerror response does not include the service data and the S-CSCF itselfjust restores from the failed status, the error response processingsub-module instructs the user information processing module to send thedisaster tolerance restoring interrogation request to the storage entityin the network and acquires the service data.

The disaster tolerance restoring indicator interrogating sub-module andthe error response processing sub-module are optional, that is, when theservice data interrogating sub-module determines that the userinformation processing module does not have any service data, theservice data interrogating sub-module can directly instruct the userinformation processing module to acquire the service data from thestorage entity in the network.

The user information processing module is connected to the registerrequest processing module and the session setup request processingmodule, and is adapted to store the service data and interact with thestorage entity in the network so as to back up and acquire the necessarydata which is required when the user service processing is restored.

Particularly, the user information processing module backs up thenecessary data which is required when the user service processing isrestored on the storage entity in the network according to aninstruction from the register request processing module, and acquiresthe necessary data which is required when the user service processing isrestored from the storage entity in the network according to aninstruction from the session setup request processing module. That is tosay, the user information processing module further includes a backupsub-module and an interrogating sub-module.

When the necessary data on the storage entity in the network backs up,the backup sub-module sends the S-CSCF address to the storage entity inthe network. When acquiring the necessary data which is required whenthe user service processing is restored is requested from the storageentity in the network, if the interrogating sub-module receives aninstruction from the disaster tolerance restoring indicatorinterrogating sub-module about sending the disaster tolerance restoringinterrogation request to the storage entity in the network and acquiringthe service data, the interrogating sub-module sends the S-CSCF addresswith the disaster tolerance restoring indicator to the storage entity inthe network. After acquiring the necessary data which is required whenthe user service processing is restored, the interrogating sub-moduleinstructs the session setup request processing module to continuouslyprocess the session setup request.

The user information processing module further includes a timer startingsub-module, which is adapted to start a disaster tolerance restoringtimer after acquiring the necessary data which is required when the userservice processing is restored.

The disaster tolerance restoring timer is adapted to count the timeafter being started, and if the user dose not initiates a registrationflow before the timeout of the disaster tolerance restoring timer, thedisaster tolerance restoring timer instructs the user informationprocessing module to perform a network deregistration on the user, thatis, to delete a data of the user. The disaster tolerance restoring timeris optional.

The storage entity in the network is usually an HSS.

FIG. 14 is a block diagram of an HSS according to an embodiment of thepresent invention.

In an HSS provided according to the present invention, two modules areincreased and modified on the basis of the existing HSS, including auser data storing module and an interrogation request processing module.

Specifically, the user data storing module is adapted to storesubscription data of a user, necessary data which is required when auser service is restored, and an S-CSCF with which the user registers.The interrogation request processing module is adapted to extractcorresponding information from the user data storing module according toan interrogation request and return the corresponding information to aparty that sends the interrogation request.

In particular, the interrogation request processing module includes anS-CSCF interrogation request determination sub-module, a disastertolerance restoring interrogation request processing sub-module, and anunregistered user interrogation request processing sub-module.

The S-CSCF interrogation request determination sub-module is adapted tojudge whether the interrogation request from the S-CSCF is a disastertolerance restoring interrogation request or an unregistered userinterrogation request, send the request to the disaster tolerancerestoring interrogation request processing sub-module for beingprocessed if it is the disaster tolerance restoring interrogationrequest; and send the request to the unregistered user interrogationrequest processing sub-module for being processed if it is theunregistered user interrogation request.

The disaster tolerance restoring interrogation request processingsub-module is adapted to extract corresponding information from the userdata storing module according to the interrogation request and returnthe corresponding information to the S-CSCF.

The unregistered user interrogation request processing sub-module isadapted to judge whether the user is registered or not according to theS-CSCF with which the user registers, and extract the correspondinginformation from the user data storing module and return thecorresponding information to the S-CSCF if the user is not registered;and return an error response to the S-CSCF if the user is registered.Under the situation that the user is registered, the HSS can alsoextract the corresponding information from the user data storing module,carries the corresponding information in the error response, and returnsthe error response to the S-CSCF.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided that theyfall within the scope of the following claims and their equivalents.

1. A method for realizing an Internet protocol multimedia subsystem(IMS) disaster tolerance, comprising: receiving, by a serving callsession control function (S-CSCF), a user registration, and backing upnecessary data which is required when a user service processing isrestored on a storage entity in a network; receiving, by aninterrogating CSCF (I-CSCF) of the user's home domain, a service requestof the user, and if it is found that the S-CSCF currently providing aservice for the user fails, assigning a new S-CSCF to the user, andforwarding the service request to the newly assigned S-CSCF; andinterrogating and acquiring, by the newly assigned S-CSCF, subscriptiondata of the user and the necessary data backed up by the original S-CSCFfrom the storage entity, and then restoring the user service processingaccording to the subscription data and the necessary data.
 2. The methodaccording to claim 1, wherein the S-CSCF sends a register successmessage carrying an S-CSCF address and an I-CSCF address to the userafter receiving the user registration, and the service request of theuser is a session setup request from the user; and the receiving, by theI-CSCF, the service request of the user, and if it is found that theS-CSCF currently providing the service for the user fails, assigning anew S-CSCF to the user further comprises: sending, by the user, thesession setup request to a proxy CSCF (P-CSCF) according to the registersuccess message, and the session setup request carries the S-CSCFaddress and the I-CSCF address which is acquired from the registersuccess message in the session setup request; forwarding, by the P-CSCF,the session setup request to the I-CSCF according to the I-CSCF addressin the session setup request; inspecting, by the I-CSCF, the status ofthe S-CSCF with which the user currently registers according to theS-CSCF address in the session setup request, and interrogating andacquiring an address of the S-CSCF currently providing the service forthe user from the storage entity after finding that the S-CSCF withwhich the user currently registers fails; and inspecting, by the I-CSCF,the status of the S-CSCF currently providing the service for the useraccording to the address of the S-CSCF returned by the storage entity,and starting to assign the new S-CSCF to the user after finding that theS-CSCF currently providing the service for the user fails.
 3. The methodaccording to claim 1, wherein the service request of the user is asession setup request sent to the user; and receiving, by the I-CSCF,the service request of the user, and if it is found that the S-CSCFcurrently providing the service for the user fails, assigning the newS-CSCF to the user further comprises: interrogating and acquiring, bythe I-CSCF, the address of the S-CSCF currently providing the servicefor the user from the storage entity; and determining, by the I-CSCF,that the S-CSCF currently providing the service for the user failsaccording to the address of the S-CSCF returned by the storage entity,and then starting to assign the new S-CSCF to the user.
 4. The methodaccording to claim 3, wherein the determining, by the I-CSCF, that theS-CSCF currently providing the service for the user fails according tothe address of the S-CSCF returned by the storage entity furthercomprises at least one of: inspecting, by the I-CSCF, the status of theS-CSCF currently providing the service for the user according to theaddress of the S-CSCF returned by the storage entity, and determiningthat the S-CSCF currently providing the service for the user failsaccording to an inspection result; and forwarding, by the I-CSCF, theservice request to the S-CSCF according to the address of the S-CSCFreturned by the storage entity, and determining that the S-CSCFcurrently providing the service for the user fails when no response isreceived from the S-CSCF after a certain time period.
 5. The methodaccording to claim 1, wherein the assigning a new S-CSCF to the userfurther comprises at least one of: interrogating, by the I-CSCF of theuser's home domain, a requirement on the capability of the S-CSCF duringa subscription of the user from the storage entity, and assigning thenew S-CSCF to the user according to the capability requirement; andassigning, by the I-CSCF of the user home domain, the new S-CSCF to theuser according to a pre-configured local S-CSCF redundancy relationtable.
 6. The method according to claim 1, wherein when the newlyassigned S-CSCF interrogates and acquiring the subscription data of theuser and the necessary data backed up by the original S-CSCF from thestorage entity, the newly assigned S-CSCF carries an address of thenewly assigned S-CSCF itself, and the storage entity records the addressof the newly assigned S-CSCF as the address of the S-CSCF currentlyproviding the service for the user.
 7. The method according to claim 6,wherein the restoring, by the newly assigned S-CSCF, the user serviceprocessing further comprises: receiving, by the I-CSCF of the user homedomain, the service request of the user once again, and interrogatingand acquiring an address of the S-CSCF currently providing the servicefor the user from the storage entity if it is found that the S-CSCF withwhich the user registers fails; sending, by the storage entity, theaddress of the S-CSCF currently providing the service for the user tothe I-CSCF; forwarding, by the I-CSCF, the service request to the S-CSCFcurrently providing the service for the user; and processing, by theS-CSCF currently providing the service for the user, the service requestof the user; or receiving, by the I-CSCF of the user home domain, theservice request sent to the user once again, and interrogating andacquiring an address of the S-CSCF currently providing the service forthe user from the storage entity; sending, by the storage entity, theaddress of the S-CSCF currently providing the service for the user tothe I-CSCF; forwarding, by the I-CSCF, the service request to the S-CSCFcurrently providing the service for the user; and processing, by theS-CSCF currently providing the service for the user, the service requestof the user.
 8. The method according to claim 1, wherein the forwarding,by the I-CSCF, the service request to the newly assigned S-CSCF furthercomprises: carrying a disaster tolerance restoring indicator in theservice request to represent that this service request is a disastertolerance restoring service request, and forwarding, by the I-CSCF, theservice request to the newly assigned S-CSCF.
 9. The method according toclaim 8, wherein the interrogating and acquiring, by the newly assignedS-CSCF, the subscription data of the user and the necessary data backedup by the original S-CSCF from the storage entity further comprises:determining, by the newly assigned S-CSCF, that this service request isa disaster tolerance restoring request according to the disastertolerance restoring indicator after receiving the service request,requesting the subscription data and the necessary data from the storageentity, and carrying an address of the newly assigned S-CSCF itself withthe disaster tolerance restoring indicator.
 10. The method according toclaim 9, wherein the storage entity records the address of the newlyassigned S-CSCF with the disaster tolerance restoring indicator as theaddress of the S-CSCF currently providing the service for the user. 11.The method according to claim 1, wherein a registration timer is set onthe user side, and between the S-CSCF receiving the user registrationand the I-CSCF receiving the service request of the user, the methodfurther comprises: triggering a re-registration when the registrationtimer on the user side is overtime, and sending a register request tothe I-CSCF; interrogating and acquiring, by the I-CSCF, an address ofthe S-CSCF currently providing the service for the user from the storageentity; determining, by the I-CSCF, that the S-CSCF currently providingthe service for the user fails according to the address of the S-CSCFreturned by the storage entity, then starting to assign the new S-CSCFto the user, and forwarding the register request to the newly assignedS-CSCF; and receiving, by the newly assigned S-CSCF, the userregistration, and ending a current flow.
 12. The method according toclaim 11, wherein the determining, by the I-CSCF, that the S-CSCFcurrently providing the service for the user fails according to theaddress of the S-CSCF returned by the storage entity further comprisesat least one of: inspecting, by the I-CSCF, the status of the S-CSCFcurrently providing the service for the user according to the address ofthe S-CSCF returned by the storage entity, and determining that theS-CSCF currently providing the service for the user fails according toan inspection result; and forwarding, by the I-CSCF, the service requestto the S-CSCF according to the address of the S-CSCF returned by thestorage entity, and determining that the S-CSCF currently providing theservice for the user fails when no response is received from the S-CSCFafter a certain time period.
 13. The method according to claim 1,wherein a registration timer is set on a user side, and after the newlyassigned S-CSCF restores the user service processing according to thesubscription data and the necessary data, the method further comprises:triggering a re-registration when the registration timer on the userside is overtime, and sending a register request to the I-CSCF;forwarding, by the I-CSCF, the register request to the newly assignedS-CSCF; and receiving, by the newly assigned S-CSCF, the userregistration.
 14. The method according to claim 1, wherein a disastertolerance restoring timer is set on the S-CSCF, and after the newlyassigned S-CSCF restores the user service processing according to thesubscription data and the necessary data, the method further comprises:starting, by the newly assigned S-CSCF, the restoring timer and judgingwhether a register request from the user is received or not before therestoring timer is overtime; accepting the user registration if theregister request of the user is received; otherwise, performing anetwork deregistration on the user.
 15. The method according to claim 1,further comprising: starting, by the I-CSCF, an acknowledgement timerfor a failed S-CSCF after finding that the S-CSCF fails; forwarding, bythe I-CSCF, a service request to the S-CSCF and adding a disastertolerance restoring indicator parameter in the service request when theI-CSCF receives the service request sent to the S-CSCF and theacknowledgement timer started for the S-CSCF is not overtime, after thefailed S-CSCF restores to a normal status; otherwise, adding no disastertolerance restoring indicator parameter in the service request; andinterrogating and acquiring, by the S-CSCF, the subscription data of theuser and the necessary data from the storage entity and restoring theuser service processing if it is found that the correlative user is notregistered on present S-CSCF and the service request contains thedisaster tolerance restoring indicator parameter after receiving theservice request.
 16. An interrogating call session control function(I-CSCF), comprising a detecting module, an assigning module and asession setup request processing module, wherein: the detecting moduleis adapted to judge, according to a received session setup request,whether a serving CSCF (S-CSCF) currently providing a service for a userfails or not; instruct the assigning module to assign a new S-CSCF forthe current user if the S-CSCF currently providing the service for theuser fails, or instruct the session setup request processing module toforward the session setup request to the S-CSCF currently providing theservice for the user if the S-CSCF currently providing the service forthe user does not fail; the assigning module is adapted to assign thenew S-CSCF to the user according to an instruction from the detectingmodule, and instruct the session setup request processing module toforward the session setup request to the newly assigned S-CSCF afterfinishing assigning the new S-CSCF; and the session setup requestprocessing module is adapted to forward the session setup requestaccording to an instruction from the detecting module or the assigningmodule.
 17. The I-CSCF according to claim 16, wherein the session setuprequest processing module further comprises: an instruction judgmentsub-module, adapted to judge whether an instruction of forwarding thesession setup request is sent from the detecting module or the assigningmodule, directly forward the session setup request if the instruction issent from the detecting module, or carry a disaster tolerance restoringindicator in the session setup request if the instruction is sent fromthe assigning module.
 18. The I-CSCF according to claim 16, wherein theassigning module comprises at least one selected from the followingsub-modules: an interrogating sub-module, adapted to interrogate acapability requirement on S-CSCFs in subscription data of the user froma storage entity in a network, and assign the new S-CSCF to the useraccording to the capability requirement; and a redundancy relationstoring sub-module, adapted to store an S-CSCF redundancy relationgroup, select one S-CSCF from the corresponding redundancy relationgroup according to an address of the S-CSCF currently providing theservice for the user, and assign the S-CSCF to the user.
 19. A servingcall session control function (S-CSCF), comprising a register requestprocessing module, a session setup request processing module and a userinformation processing module, wherein: the register request processingmodule is adapted to send a self address and an address of aninterrogating CSCF (I-CSCF) of a current domain to a user when a userregistration is accepted, store service data of the user in the userinformation processing module, and instruct the user informationprocessing module to back up necessary data which is required when auser service processing is restored on a storage entity in a network;the session setup request processing module is adapted to process areceived session setup request according to user information; and theuser information processing module is connected to the register requestprocessing module and the session setup request processing module, andis adapted to store the service data, and interact with the storageentity in the network so as to back up and acquire the necessary datawhich is required when the user service processing is restored.
 20. TheS-CSCF according to claim 19, wherein the session setup requestprocessing module comprises a service data interrogating sub-module anda session setup request forwarding sub-module, wherein: the service datainterrogating sub-module is adapted to interrogate whether the userinformation processing module has the service data or not; and send thesession setup request to the session setup request forwarding sub-moduleif the user information processing module has the service data, andinstruct the user information processing module to acquire the servicedata from the storage entity in the network if the user informationprocessing module has not the service data; and the session setuprequest forwarding sub-module is adapted to forward the session setuprequest according to the service data.
 21. The S-CSCF according to claim19, wherein the user information processing module further comprises: abackup sub-module, adapted to back up the necessary data which isrequired when the user service processing is restored on the storageentity in the network according to an instruction from the registerrequest processing module, and send an address of the S-CSCF to thestorage entity in the network; and an interrogating sub-module, adaptedto acquire the necessary data which is required when the user serviceprocessing is restored from the storage entity in the network accordingto an instruction from the session setup request processing module. 22.The S-CSCF according to claim 19, further comprising: a disastertolerance restoring timer, connected to the user information processingmodule, and adapted to count the time after being started; and instructthe user information processing module to perform a networkderegistration on the user, that is, to delete data of the user if theuser does not initiate a registration flow before the disaster tolerancerestoring timer is overtime; and the user information processing modulefurther comprising: a timer starting sub-module, adapted to start thedisaster tolerance restoring timer after acquiring the necessary datawhich is required when the user service processing is restored.
 23. TheS-CSCF according to claim 19, wherein the session setup requestprocessing module comprises a service data interrogating sub-module, adisaster tolerance restoring indicator interrogating sub-module, anerror response processing sub-module and a session setup requestforwarding sub-module, wherein: the service data interrogatingsub-module is adapted to interrogate whether the user informationprocessing module has the service data or not, and send the sessionsetup request to the session setup request forwarding sub-module if theuser information processing module has the service data, or send thesession setup request to the disaster tolerance restoring indicatorinterrogating sub-module if the user information processing module hasnot the service data; the disaster tolerance restoring indicatorinterrogating sub-module is adapted to judge whether the session setuprequest has a disaster tolerance restoring indicator or not, andinstruct the user information processing module to send a disastertolerance restoring interrogation request to the storage entity in thenetwork and acquire the service data if the session setup request hasthe disaster tolerance restoring indicator, or instruct the userinformation processing module to send an unregistered user interrogationrequest to the storage entity in the network and acquire the servicedata if the session setup request does not have the disaster tolerancerestoring indicator; the error response processing sub-module is adaptedto judge whether an error response contains the service data or notafter receiving the error response sent from the storage entity in thenetwork, and instruct the user information processing module to send thedisaster tolerance restoring interrogation request to the storage entityin the network and acquire the service data when the error response doesnot contain the service data and the S-CSCF itself is restored from afailure; and the session setup request forwarding sub-module is adaptedto forward the session setup request according to the service data. 24.The S-CSCF according to claim 23, wherein the user informationprocessing module further comprises: a backup sub-module, adapted toback up the necessary data which is required when the user serviceprocessing is restored on the storage entity in the network according toan instruction from the register request processing module, and send anS-CSCF address to the storage entity in the network; and aninterrogating sub-module, adapted to acquire the necessary data which isrequired when the user service processing is restored from the storageentity in the network according to an instruction from the session setuprequest processing module, and send an address of the S-CSCF with thedisaster tolerance restoring indicator to the storage entity in thenetwork when the disaster tolerance restoring indicator interrogatingsub-module instructs to send the disaster tolerance restoringinterrogation request to the storage entity in the network and acquiresthe service data.
 25. A home subscriber server (HSS), comprising a userdata storing module adapted to store subscription data of a user,necessary data which is required when a user service is restored and aregistered serving call session control function (S-CSCF), or furthercomprising an interrogation request processing module, wherein theinterrogation request processing module comprises an S-CSCFinterrogation request determination sub-module, a disaster tolerancerestoring interrogation request processing sub-module and anunregistered user interrogation request processing sub-module, wherein:the S-CSCF interrogation request determination sub-module is adapted tojudge whether an interrogation request from the S-CSCF is a disastertolerance restoring interrogation request or an unregistered userinterrogation request, send the request to the disaster tolerancerestoring interrogation request processing sub-module for beingprocessed if the interrogation request is the disaster tolerancerestoring interrogation request, and send the request to theunregistered user interrogation request processing sub-module for beingprocessed if the interrogation request is the unregistered userinterrogation request; the disaster tolerance restoring interrogationrequest processing sub-module is adapted to extract a correspondinginformation from the user data storing module according to theinterrogation request and return the corresponding information to theS-CSCF; and the unregistered user interrogation request processingsub-module is adapted to judge whether the user is registered or notaccording to the S-CSCF with which the user registers, and extract thecorresponding information from the user data storing module and returnthe corresponding information to the S-CSCF if the user is notregistered, or return an error response to the S-CSCF if the user isregistered.
 26. The HSS according to claim 25, wherein if the user isregistered, the unregistered user interrogation request processingsub-module extracts the corresponding information from the user datastoring module, carries the corresponding information in the errorresponse, and returns the error response to the S-CSCF.
 27. A method forrealizing an Internet protocol multimedia subsystem (IMS) disastertolerance, comprising: receiving, by a serving call session controlfunction (S-CSCF), a user registration, saving service data of a user,and backing up necessary data which is required when a user serviceprocessing is restored on a storage entity in a network; and accepting,by the S-CSCF, a service request of the user after the service data ofthe user is lost, interrogating and acquiring subscription data of theuser and the backup necessary data from the storage entity, and thenprocessing the service request of the user according to the subscriptiondata and the backup necessary data.
 28. The method according to claim27, wherein the interrogating and acquiring, by the S-CSCF, thesubscription data of the user and the backup necessary data from thestorage entity further comprises: sending, by the S-CSCF, anunregistered user interrogation request to the storage entity;determining, by the storage entity, that the user is registeredaccording to the subscription data of the user, and returning an errorresponse to the S-CSCF; and sending, by the S-CSCF, a disaster tolerancerestoring interrogation request to the storage entity according to theerror response so as to acquire the subscription data of the user andthe backup necessary data; or sending, by the S-CSCF, an unregistereduser interrogation request to the storage entity; and determining, bythe storage entity, that the user is registered according to thesubscription data of the user, returning an error response to theS-CSCF, and carrying the subscription data of the user and the backupnecessary data in the error response.